Illumination burner

ABSTRACT

A gas illuminating burner in which a gas mixture is delivered through a porous ceramic support and a heat radiating layer of a metal oxide to a layer which is a mixture of thorium and cerium oxides. The gas mixture burns in an improved manner at the upper surface of the layer of oxides.

Ilnited States Patent 1 Reid et a1.

[ ILLUMINATION BURNER [75] Inventors: Jack M. Reid; Sanford A. Weil;

I David M. Mason; William R. Staats,

all of Chicago, Ill.

[73] Assignee: The Institute of Gas Technology,

Chicago, Ill.

[22] Filed: Oct. 20, 1969 [21] App]. No: 867,482

[52] U.S. Cl. 431/328 [51] Int. Cl F23d 13/12 [58] Field of Search431/328, 329, 100

[56] References Cited UNITED. STATES PATENTS 3,170,504 2/1965 Lanning431/328 June 12, 1973 3,208,247 9/1965 Wei] et a1. 431/328 3,216,47811/1965 Saunders et al. 431/329 3,304,402 2/1967 Thorpe 118/302 X3,367,149 2/1968 Manske 431/328 Primary Examiner-Carroll B. Dority, Jr.

. Attorney-Dominik, Knechtel 8L Godula [57] ABSTRACT A gas illuminatingburner in which a gas mixture is delivered through a porous ceramicsupport and a heat radiating layer of a metal oxide to a layer which isa mixture of thorium and cerium oxides. The gas mixture burns in animproved manner at the upper surface of the layer of oxides.

1 Claim, 3 Drawing Figures Pmmiow m 3,739,793

IN VE /V 7' 0/?5 Jack M. Reid Sanford A. Well David M. Mason By WilliamR. .Sfaafs ATTYS.

1 ILLUMINATION BURNER This invention relates to a burner for producingillumination by gas combustion and more particularly to the productionof efficient illumination by the combustion of conventional fuel gas.

In U. S, Pat. No. 3,208,247, there is disclosed a burner for producingillumination by gas which is formed of a relatively thick plate or sheetof porous ceramic, preferably thorium oxide, having a thin layer at itsouter surface formed by a mixture of thorium oxide and cerium oxide. Thegaseous fuel coupled to the burner flows from and burns on the outersurface of the plate or sheet of porous ceramic.

The burner of this subject patent has demonstrated that the fragileproperties of the conventional mantle can be overcome, while stillretaining the very critical thermal characteristics of a mantle-flamesystem. The burner, however, does suffer several disadvantages whichrender it less than satisfactory, or at least eco nomically feasible.For example, one problem with the burner is that it is extremelydifficult to establish or maintain a stable flame so that the thoriumoxide and cerium oxide layer is' maintained at a high temperature so asto produce or provide the maximum light output.

, Another disadvantage-of the subject burner is.that

the plate or sheet'of porous ceramic is composed entirely of thoriumoxide, and this material is relatively costly. Also, it is verydifficult to manufacture the thorium oxide with the desired physicalproperties because of the refractoriness of thorium oxide. In order toretain the necessary thermal properties, the effective materialthickness of the bubblesor cells, or the diameter of the fibers, must bekept below 0.005 inches. At the same time, the material must be wellsintered in order to develop the desired mechanical strength of theplate or sheet. The fact that the melting point of thorium oxide issubstantially higher than'any other refractory material (5,486 F),however, makes it extremely difficultto obtain a satisfactory degree ofsintering, without destroying the very thin plate or sheet of porousceramic. The end result is that the extreme care required to achieve theprecise results'desired, together with the relatively large quantity ofthorium oxide required compared to the amount actually contributing toemission oflight, result in a relatively costly burner.

Accordingly, it is an object of the present invention to provide animproved burner and method for making the same. s

Another object is to provide an improved burner fabricated in a fashionsuch that the desired structural and thermal properties are easily andeconomically achieved.

Still another object is to provide an improved burner burner constructedina fashion such as to permit or provide better control of the flamezone so that the burner surface is maintained at a high temperature.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

' The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings in which:

'FIG. 1 is a sectional view of a gas burner exemplary of the invention;

FIG. 2 is a sectional view taken along lines 2-2 of FIG. 1; and

FIG. 3 is an enlarged view of the burner plate of the gas burner.

Similar reference characters refer to similar parts throughout theseveral views of the drawings.

Referring'now to the drawing, in FIG. 1 there is illustrated a gasburner 10 exemplary of the invention including a burner plate 11 in theform of a relatively thick flat plate which may be circular, or of otherdesired configuration. The burner plate 11 is supported in a cup-shapedhousing 12 having a connection 13 at one end for admission ofcombustible gas and air mixture. Preferably the cup-shaped body isprovided with an annular. outer flange 14 encircling the outer edge ofthe burner plate 11 to prevent gas from flowing through the sides of theburner plate.

The burner plate 11, as can be best seen in FIGS. 2 and 3, is formed ofa lower layer or body 15 of any suitable porous ceramic material,preferably one having a number of parallel passages similar to ahoneycomb in nature, as illustrated in FIG. 3, through which thecombustible-gas mixture can flow. Advantageously, the ceramic materialis one having good thermal and mechanical shock resistance. Also, itsease of fabrication and cost should be considered. A suitable materialwhich can be used is Tl-IERMACO'MB, manufactured by the Minnesota Miningand Manufacturing Company. This layer or body 15 should be approximately54; inch in thickness in order that it will have a relatively highmechanical strength even apart from the insulating factor. Bymaintaining the inner surface of the body 15 relatively cool, radiationtherefrom is minimized so that greater efficiency will result.

A layer 16 of thorium oxide is atop the ceramic body 15. This layer mustbe opaque and therefore at least 0.2 mm. in thickness so that it willfunction as an insulator between the upper combustion area and the body15, where radiation would be the major heat transfer mechanism. Again,this is to prevent the body 15 from becoming sufficiently'hot to radiatein the IR region. This thorium oxide layer also must be of very smallgrains or particles, at least 2 microns in diameter, in order toproperly insulate the body 15 from the upper combustion area. I

The next layer atop the thorium oxide layer 16 is a metal oxide layer 17having emissivity of the order of 0.5 so that it radiates enough heat tostabilize the combustion process. The metal oxide may be alumina, forexample. This metal oxide layer need only be 1 mm. or

less in thickness.

Atop the metal oxide layer 17 is a layer 18 of a mixture of thoriumoxide and cerium oxide. This layer 18 should contain 0.0002 grams ofcerium oxide per square centimeter and be less than 0.5 mm. thick. The

particles in this layer must be at least 0.2 microns more in diameter.

In operation, the combustible gas and air mixture is admitted into thehousing 12 through the connection 13 and flows through the burner plate11. When ignited, the combustible gas mixture burns at the surface ofthe thorium oxide and cerium oxide layer 18 and heats the latter toproduce radiation of illumination therefrom.

The metal oxide layer 17 overcomes the problem of the gas burnerdisclosed in the above-mentioned U. S. Pat. No. 3,208,247, ofmaintaining a stable flame. With the addition of this metal oxide layer,it is found that a more stable flame can be maintained, and the thoriumoxide and cerium oxide layer 18 deposited atop of it is maintained at ahigh temperature so that the maximum radiation of illumination isprovided.

The thorium oxide layer 16 and the thorium oxide and cerium oxide layer18 both preferably and advantageously are deposited by flame spraying,or by plasma spraying them. Alternatively, however, these layers can beformed and deposited in the same manner as described in theabove-mentioned U. S. Pat. No. 3,208,247. That is, the thorium oxidelayer 16 can be formed by absorbing a solution of a water solublethorium salt, such as thorium nitrate, in a combustible material havingthe desired physical structure, such as sponge foam or felt. Thematerial may then be heated to a sufficiently high temperature in afurnace, or the like, to burn out the combustible material and toconvert the thorium solution to a residue of thorium oxide with a porousstructure conforming to that of the original combustible material. Theheating process is preferably carried out at a temperature slightlybelow the melting point of the thorium oxide so that the residualthorium oxide will sinter to form a body or layer of relatively highstrength. The thorium oxide and cerium oxide layer 18 can be formed byfirst forming a thorium oxide layer in the manner described above, then,a cerium salt, such as cerium nitrate, is deposited in a thin layer onthe surface of the thorium oxide layer as by dipping the surface in asolution of the cerium salt. After dipping, the burner plate is airdried at an elevated temperature of about 1000 F to decompose the ceriumsalt to cerium oxide and leave the cerium oxide mixed with the thoriumoxide.

The metal oxide layer l7can be deposited in any suitable fashion.

The gas burner has all of the advantages of the gas burner disclosed inthe above-mentioned U. S. Pat. No. 3,208,247 and, in addition, has thefurther advantage of better flame control so that the thorium oxide andcerium oxide layer 18 is maintained at a high temperature so as toprovide maximum radiation of illumination therefrom. Furthermore, thegas burner 10 is fabricated in a fashion such that the desiredstructural and thermal properties are more easily and more economicallyachieved.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained andcertain changes may be made in the above construction. Accordingly, itis intended that all matter contained in the above description or shownin the accompanying drawings shall be interpreted as illustrative andnot in a limiting sense.

Now that the invention has been described, what is claimed as new anddesired to be secured by Letters Patent is:

1. An illumination burner for producing illumination by gas combustioncomprising: a burner plate formed of a porous ceramic material throughwhich the combustible gas mixture can flow, said burner plate havinggood thermal and mechanical shock resistance and being of a thicknesssuch as to have a high mechanical strength apart from its insulatingfactor; a layer comprising a mixture of thorium oxide and cerium oxidedeposited on said burner plate, said layer being less than 0.5 mm thick;conduit means to conduct a combustible gas mixture to said burner plate,the gas mixture flowing through said burner plate and burning at theupper surface of said mixture of thorium oxide and cerium oxide tothereby heat the latter to produce radiation of illumination therefrom,a layer of insulating material deposited atop said burner plate forinsulating said burner plate from the combustion area of said gasmixture to prevent said burner plate from becoming sufficiently hot toradiate in the infrared region, said layer of insulating material beingof thorium oxide and at least 0.2 mm in thickness; a layer of heatradiating material deposited atop said layer of insulating materialbeneath said layer of thorium oxide and cerium oxide, said layer of heatradiating material being a metal oxide having emissivity of the order of0.5 so as to radiate heat to maintain said mixture of thorium oxide andcerium oxide at a high temperature to provide maximum radiation ofillumination therefrom and to stabilize the combustion process.

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